1. Field of the Invention
The present invention relates to a document management system and method thereof for retrieving a related document.
2. Description of the Related Art
Recently, a document management system (a document browsing system) which can retrieve a related document has been proposed.
For example, in the document browsing system described in Japanese Patent Laid-Open No. 10-269237, a keyword is extracted from a browsed document, by referring to keyword information registered beforehand, according to a field, a user etc., and the related document is retrieved using the extracted keyword.
However, in the above-described document browsing system, a user keyword must be defined beforehand for every user. Therefore, in Japanese Patent Laid-Open No. 10-269237, it is necessary to spend time and effort registering a user's keyword in advance.
In addition, since the keyword information is exclusive to each user, there is the limitation that keyword information is unsharable among different users. Also, since the retrieval of the related document is performed for all documents stored in a document database, retrieval of the related document is not efficient. Since the keyword information for every user is stored by the relational database, there is a problem that, when information related to a user is added, a table or a column must be added for the database and a system which accesses it must be modified.